In philosophical discourse, flourishing is widely thought to require the development and exercise of virtues. Positive psychology, as the science of happiness and flourishing, should, therefore, include the scientific investigation of the virtues. However, the main classification of virtues and strengths, the Values in Action Inventory of Strengths (VIA-IS), faces major criticisms that, if not addressed, may undermine the credibility of positive psychology as a science. One such criticism is that virtue-based classifications lack a conceptual foundation; another is that these classifications may harm individuals by attaching potentially stigmatising labels to them. In this paper, we propose that positive psychologists can address these critiques by taking an interdisciplinary approach, which involves adopting a philosophically rich Aristotelian theory of virtue, and further developing this approach through empirical research. Adopting a philosophical theory will provide a strong conceptual base for psychologists, guiding the construction of measures and the formation of hypotheses about virtues. However, as many scholars acknowledge, it is difficult to measure all aspects of Aristotelian virtues, such as emotions, reasons, and attitudes. Another aim of this paper is, therefore, to suggest appropriate methods for measuring these aspects of Aristotelian virtues.